Fluid accelerator for use with an hydraulic jar in a well

ABSTRACT

An accelerator for use with an hydraulic jar in a well for storing energy immediately above the jar and drill collars, including piston means for compressing a fluid on one side thereof to develop stored energy on the jarring stroke, and means for transferring fluid from the other side of the piston means to said one side thereof upon the return stroke of the jar.

United States Patent [111 3,570,612

[72] Inventor Damon T. Slator [56] References Cited H UNITED STATESPATENTS [211 PP 763,363 2,988,147 6/1961 Webb 175/297x [22] Filed Oct.17, 1968 3,088,533 5/1963 Sutliff 175/297 3 i t f iz 3,251,426 5/1966LeBourg 175/297 1 sslgnee 3,353,613 11/1967 Harrison 175/293 3,399,7419/1968 Monroe 175/297 3,405,773 10/1968 Sutliff 175/297 PrimaryExaminer-Nile C. Byers, Jr. Attorney-Pravel, Wilson & Matthews [54]FLUID ACCELERATOR FOR USE WITH AN ABSTRACT: An accelerator for use withan hydraulic jar in a 25:: {a g well for storing energy immediatelyabove the jar and drill colm a mg g lars, including piston means forcompressing a fluid on one U.S.Cl 175/297 side thereof to develop storedenergy on the jarring stroke, E2lb1/06 and means for transferring fluidfrom the other side of the Field of Search 175/297, piston means to saidone side thereof upon the return stroke of 293; 267/71 the jar.

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PATENTED MARI 61971 SHEET 2 OF 3 INV EN TOR flTTORNE YS 00700 7. J/a forBY Magda mum! WEIAW & MaHLewA FLUID ACCELERATOR FOR USE WITH ANHYDRAULIC JAR IN A WELL BACKGROUND OF THE INVENTION The field of thisinvention is accelerators for use with hydraulic jars in a well.

In 1960, U.S. Pat. No. 2,953,352 wasgranted to D. D. Webb for anaccelerator wherein a compressible fluid was compressed to store energyon the jarring stroke of an hydraulic jar. Such accelerator served toaccumulate tensile energy upon the upstroke of the jar rather thandistributing the tensile energy through the full length of the pipestring being pulled. Such localized accumulation of the tensile energyin the accelerator made it possible to develop an adequate jarring blowwith the'hydraulic jar in relatively shallow well depths, and also incrooked well bores which prevent a full stretching of the pipe string.Additionally, the accelerator served to isolate the jarring impact sothat it was not transmitted to equipment at the surface.

However, such Webb accelerator suffers from the disadvantage that itproduces a partial vacuum below the piston in the accelerator as thefluid is compressed during the jarring stroke of the jar; the partialvacuum creates a pressure differential across the piston which inducesleakage of fluid to the reduced pressure. Then, upon a return of thepiston for another stroke, the fluid trapped below the piston causesexcessive pressure which either bursts the fluid seals or prevents afull closing of the tool.

The Harrison U.S. Pat. No. 3,353,613 discloses an accelerator which isan attempt to solve the problems of the Webb accelerator. However,Harrisons accelerator introduces other problems in its attempt to solvethe problems of the Webb accelerator. Harrison provided an acceleratorwherein one side of the piston is exposed to well pressure so that apartial vacuum is not produced, but the well pressure acts to partiallyclose the accelerator before the jarring stroke. Such partial closingcan be extremely detrimental, particularly in deep wells where the wellpressure is high, since the force which can be developed in theaccelerator is reduced in direct proportion to he well pressure.

SUMMARY OF THE INVENTION The present invention overcomes thedisadvantages of the accelerators in both the Webb patent and theHarrison patent. Thus, the accelerator of this invention is unafiectedby well depths and pressures as is the Harrison device, but at the sametime, the problem of trapping liquid below the piston on the returnstroke of the jar as in the Webb device is eliminated. The presentinvention produces these advantages by means of a floating piston whichcompresses the liquid on the jarring stroke of the jar therewith, butwhich moves on the return stroke to permit fluid below the piston topass above the piston rather than being trapped, whereby damage to thefluid seals is prevented and full closing is not obstructed.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a view, partly in elevationand partly in section, illustraing the accelerator of this invention;

FIGS. 2A, 2B, 2C and 2D are vertical sectional views of one-half of theaccelerator of H6. 1 from substantially the upper portion thereof to thelower portion thereof, and with the piston of the accelerator disposedin position for the upstroke;

FIG. 3 is a view similar to FIG. 2C, but illustrating the piston in theraised position for transferring fluid during the downstroke of theapparatus; and

FIG. 4 is a partial cross-sectional view taken on line 4-4 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT In .the drawings, the letter Adesignates generally the accelerator of this invention which a threadedupper end 10 for connection to a conventional pipe string (not shown) ina well, and a lower threaded pin 12 for connection with conventionaldrill collars (not shown) therebelow in the well. A typical hydraulicjar is then disposed below the drill collars, as is well understood. Aswill be explained hereinafter, the accelerator A is so constructed thatthe tensile energy stored therein by the compression of compressiblenoncombustible liquid is unaffected by the depth of the well and thepressure of the fluid in the well. Additionally, the apparatus A hasmeans for transferring fluid during the return or downstroke of theaccelerator A so as to prevent a trapping of liquid by the piston tothereby prevent damage to the seals and to also prevent interferencewith a full closing of the accelerator A, as will be more evidenthereinafter.

The accelerator A includes an outer housing 15, which in the form of theinvention illustrated in the drawings, has the threaded pin 12 at itslower end. A hollow mandrel 20 is longitudinally slidably disposedwithin the bore of the housing 15, and such mandrel 20 has the threadedbox 10 formed at its upper end in the preferred form of the invention asillustrated in FIG. 1.

The housing 15 and the mandrel 20 are suitably splined together bysplines 15a on the housing 15 and grooves or splines 20a on the mandrel20 so as to permit relative longitudinal movement therebetween whileproviding for the transmission of rotational movement from the mandrelto the housing 15 if such is desired.

An upper seal 22 is provided by one or more resilient seal rings whichmay be formed of rubber or other suitable sealing material and which arepreferably disposed between the upper end of the mandrel 20 and thehousing 15 (FIGS. 1 and 2A). A lower seal 23 which is essentially thesame as the seal 22 is formed at the lower end of the housing I5 forforming a seal between the mandrel 20 and the housing 15 (FIGS. 1 and2C). It is to be noted that the housing 15 is illustrated as beingformed in a plurality of separate parts, and likewise the mandrel 20 isillustrated as being formed in several parts, which is for assemblypurposes and it is to be understood that the invention is not limited tohaving each formed in a plurality of parts since either may be formed ina single part except for assembly purposes.

A piston P (FIGS. 1, 2C and 3) is mounted on the mandrel 20 for limitedlongitudinal movement relative to such mandrel 20. The piston P isformed of metal and is flared or tapered outwardly at its upper end sothat its annular lip 25 is adapted to provide a flexible metal-to-metalseal with the bore 15b of the housing 15. By reason of the externallytapered surface 26, only the lip 25 actually engages the bore 15b so asto minimize the frictional resistance therebetween. The flexibility ofthe lip 25 assures an adequate seal during the upstroke of the piston Pfor compressing the liquid which is thereabove. It is to be noted thatthe external surface of the mandrel 20 is spaced from the internalsurface or bore 15b of the housing 15 so as to provide an annular spacetherebetween which serves as a chamber 30 in which a compressiblenoncombustible fluid such as silicone liquid is disposed. The upper seal22 and the lower seal 23 thus confine the compressible liquid within thechamber 30 and prevent any communication with well fluid.

In the preferred form of the invention, a fluid transfer sleeve 35 ismounted on the mandrel 20 between the mandrel 20 and the piston P. Suchsleeve 35 is also preferably mounted in conjunction with a seat ring 36.The sleeve 35 and the set ring 36 are assembled on the mandrel 20between a threaded sleeve 20a which forms a lower part of the mandrel20, and an upper threaded sleeve 38 which is threaded on the mandrel 20and which has an upper surface 38a which provides an upper limit to themovement of the mandrel 20 with respect to the housing 15 should suchsurface 38a ever engage a shoulder on the housing I5.

The sleeve 35 has a lower external surface 350 which has a diametercorresponding substantially to the internal diameter 27 of the piston P.An enlarged external diameter is provided at the upper portion 35b ofthe sleeve 35 so as toform an annular laterally extending shoulder orstop 350 which is adapted to be engaged by a shoulder 28 on the piston Pto limit the upward movement of the piston P relative to the sleeve 35and the mandrel 20. A plurality of longitudinally extending slots 35dare formed in the external surface of the sleeve 35, but such slots 35dterminate at a lower shoulder 35a (FIG. 2C) so that fluid cannot passinwardly of the piston P when the piston P is in the seated position ofFIG. 2C. The lower annular surface 29 of the piston P may be termed aseating surface since it is adapted to engage the upper lateral surfaceof the seating ring 36 to form a seal therewith to prevent the flow offluid from above the piston P to the area in the chamber 30 therebelowduring the jarring stroke with the hydraulic jar used with theaccelerator A of this invention.

The grooves or recesses 35d serve as pocket means to trap foreignparticles such as small pieces of metal, rubber or the like which may bepresent inadvertently in the compressible liquid in the chamber 30. Bytrapping the particles in the recesses 35d, they are prevented frompassing to the seating surface 29 and the upper surface 36a of theseating ring 36 so as to prevent any obstruction or interference with aproper seating and sealing between such surfaces during the jarringstroke with the hydraulic jar, and thus during the upstroke with theaccelerator A.

In the operation or use of the accelerator A of this invention, it isconnected in the pipe string (not shown) above the drill collars and thehydraulic jar (not shown). At the beginning of the jarring stroke, thepiston P is in the first or lowermost position illustrated in FIG. 2Cand is ready for the compression stroke. Thus, as the pipe string ispulled upwardly, the mandrel 20 is moved upwardly, but the housing movesat a slower rate since it is connected to the hy rhulic jar. Thus, thereis relative upward-movement of the piston P and the mandrel relative tothe housing 15, and since the liquid above the piston P cannot passtherebelow, such liquid is compressed in the known manner to storetensile energy within the accelerator A.

When the hydraulic jar reaches the upper end of its pulling stroke andis released from the restriction, the housing 15 is likewise releasedand then the stored energy of the compressed fluid within the chamber istransmitted to the housing 15 to cause it to move rapidly upwardly andthus accelerate the jarring action with the hydraulic jar therebelow.

The hydraulic jar and the accelerator A are then returned to theirlowermost positions for repeating the jarring stroke with the jar.During such lowering or return movement of the accelerator A, thehousing 15 is prevented from moving downwardly by reason of the jarhaving reached in its lowermost position so that the mandrel 20 may thenmove downwardly relative to the housing 15. During the downward movementof the mandrel 20 relative to the housing 15, the flexible metal lip 25of the piston P has sufficient frictional engagement with the bore 15bof the housing 15 to cause the piston P to move to the uppermostposition shown in FIG. 3. In that position, any fluid which is below thepiston P may pass upwardly through the passages or slots d to the areaabove the piston P. Thus, any fluid which might have leaked past thepiston P during the upstroke thereof may be returned to the area abovethe piston P to avoid applying excessive pressure to the seals.23 or theother seals in the apparatus A during the return stroke of the piston Pto its lowermost position. Also, by allowing the transfer of the fluid,if any, which is below the piston P to the area thereabove during thereturn stroke of the piston P, the full closing of the piston P, or thefull return of the piston P to its lowermost or starting position isunobstructed by any collected fluid below the piston P.

I claim: 1. An accelerator for use with a hydraulic jar in a well,comprising:

a. an outer housing; b. a hollow mandrel disposed in said housing andslidable relative thereto; c. the exterior of said mandrel being spacedfrom the interror of said housing to form an annular chambertherebetween;

an upper seal between said mandrel and said housing at the upper end ofsaid chamber;

e. a lower seal between said mandrel and said housing at the lower endof said chamber;

f. a piston mounted on said mandrel for longitudinal movement relativethereto and disposed in said chamber between said upper seal and saidlower seal;

g. compressible liquid in said chamber adapted to be compressed on oneside of said piston during relative movement of said piston in onelongitudinal direction with respect to said housing;

b. means for transferring liquid in said chamber from the other side ofsaid piston to said one side thereof upon a relative movement of saidpiston in the other longitudinal direction with respect to said housing;

h. means on said mandrel and engageable with said piston for limitinglongitudinal movement of said piston relative to said mandrel between afirst position and a second position; I i

i. said piston and said mandrel having passage means associatedtherewith for establishing fluid flow from one side of said piston tothe other when said piston is in said first position; and

j. means on said mandrel engageable with said piston for closing offfluid flow through said passage means when said piston is in said secondposition for compressing the liquid as said piston and mandrel move insaid one longitudinal direction relative to said housing.

2. The structure set forth in claim 1, including a. pocket means betweensaid mandrel and said piston for collecting foreign particles in thecompressible liquid when said piston is in said second position.

3. The structure set forth in claim 1, wherein:

a. said means for closing off fluid flow through said passage meansincludes 1. a seating element mounted on said mandrel; and

2. a seating surface on said piston adapted to engage said seatingelement and fonn a seal therewith.

4. The structure set forth in claim 1, wherein:

a. said piston is annular; and

b. said means for transferring liquid includes:

1. a sleeve on said mandrel between said piston and said mandrel; and

2. passage means formed in said sleeve for the flow of the liquidtherethrough from said other side to said one side of said piston whensaid piston moves in said other longitudinal direction. 5. The structureset forth in claim 1, wherein a. said piston is annular and is formedwith an annular outwardly flared flexible metal sealing lip formetal-to-metal sealing engagement with the metallic bore of saidhousing.

6. The structure set forth in claim 1, wherein:

a. said movement of said piston in said one longitudinal directionoccurs during the jarring stroke of the hydraulic jar; and

b. the transfer of the liquid with said means for transferring liquidoccurs during the return stroke of the hydraulic jar.

1. An accelerator for use with a hydraulic jar in a well, comprising: a.an outer housing; b. a hollow mandrel disposed in said housing andslidable relative thereto; c. the exterior of said mandrel being spacedfrom the interior of said housing to form an annular chambertherebetween; an upper seal between said mandrel and said housing at theupper end of said chamber; e. a lower seal between said mandrel and saidhousing at the lower end of said chamber; f. a piston mounted on saidmandrel for longitudinal movement relative thereto and disposed in saidchamber between said upper seal and said lower seal; g. compressibleliquid in said chamber adapted to be compressed on one side of saidpiston during relative movement of said piston in one longitudinaldirection with respect to said housing; h. means for transferring liquidin said chamber from the other side of said piston to said one sidethereof upon a relative movement of said piston in the otherlongitudinal direction with respect to said housing; h. means on saidmandrel and engageable with said piston for limiting longitudinalmovement of said piston relative to said mandrel between a firstposition and a second position; i. said piston and said mandrel havingpassage means associated therewith for establishing fluid flow from oneside of said piston to the other when said piston is in said firstposition; and j. means on said mandrel engageable with said piston forclosing off fluid flow through said passage means when said piston is insaid second position for compressing the liquid as said piston andmandrel move in said one longitudinal direction relative to saidhousing.
 2. The structure set forth in claim 1, including a. pocketmeans between said mandrel and said piston for collecting foreignparticles in the compressible liquid when said piston is in said secondposition.
 2. a seating surface on said piston adapted to engage saidseating element and form a seal therewith.
 2. passage means formed insaid sleeve for the flow of the liquid therethrough from said other sideto said one side of said piston when said piston moves in said otherlongitudinal direction.
 3. The structure set forth in claim 1, wherein:a. said means for closing off fluid flow through said passage meansincludes
 4. The structure set forth in claim 1, wherein: a. said pistonis annular; and b. said means for transferring liquid includes:
 5. Thestructure set forth in claim 1, wherein a. said piston is annular and isformed with an annular outwardly flared flexible metal sealing lip formetal-to-metal sealing engagement with the metallic bore of saidhousing.
 6. The structure set forth in claim 1, wherein: a. saidmovement of said piston in said one longitudinal direction occurs duringthe jarring stroke of the Hydraulic jar; and b. the transfer of theliquid with said means for transferring liquid occurs during the returnstroke of the hydraulic jar.